[Linux/Regression] Segfault with --ozone-platform=x11 when KDE Global Menu is active

Does this issue occur when all extensions are disabled?: Yes

### Environment:
- VS Code Version: 1.136 (Worked in 1.135)
- OS Version: Ubuntu 26.04
- KDE Plasma Version: 6.6.6
- KDE Frameworks Version: 6.24.0
- Qt Version: 6.10.2
- GNOME Shell Version: 50.1
- Kernel Version: 7.0.0-30-generic (64-bit)
- Graphics Platform: Wayland

### Summary (Regression):
Launching VS Code 1.136 with `--ozone-platform=x11` crashes with `Segmentation fault (core dumped)` when KDE's Global Menu widget is active.

### Reproduction Steps:
1. In KDE Plasma, add the Global Menu widget to the top panel.
2. Launch VS Code 1.136, Segfault occurs immediately or fails during DBusMenu event loop:
```
$ ./code --no-sandbox --ozone-platform=x11
Segmentation fault (core dumped) ./code --no-sandbox --ozone-platform=x11
```

### Root Cause / Logs:
The issue is isolated to the D-Bus AppMenu / GObject signal registration in the Ozone-X11 backend.
When the Global Menu widget is removed (or under pure GNOME without DBusMenu listener), VS Code launches fine.
When the Global Menu is present, it triggers dangling signal handler errors or immediate segfaults:
```
(code:149279): LIBDBUSMENU-GLIB-WARNING **: About to Show called on an item wihtout submenus. We're ignoring it.
[149279:0903/005611.257265:ERROR:content/browser/browser_main_loop.cc:274] GLib-GObject: ../../../gobject/gsignal.c:2723: instance '0x2c94019eebd0' has no handler with id '6742'
```